Conventional pumps—specifically centrifugal or axial pumps—comprises a rotatable impeller mounted onto a drive shaft, which impeller must be interconnected to the drive shaft in a suitable way that provides a rigid and non-rotational connection. At the same time it should be possible to adjust the axial location of the impeller in relation to the drive shaft, in order to adjust the location of the impeller in relation to the impeller seat when the impeller wears.
One known way to interconnect a first element and a second element to each other in order to transmit a rotational motion, is to use a key and key-way joint, which comprises a key that is inserted into opposite key-ways in the respective elements. Such a joint is often to a great extent appropriate but it is often difficult to release the elements from each other without damaging them, it is also difficult to adjust the mutual axial location of the elements.
Another known way to interconnect a first and a second element to each other, is to use a tubular shaped socket, e.g. as is shown in EP 1,026,405. The socket is inserted into a centrally located recess in an impeller and then a drive shaft is inserted into said socket. The impeller is forced towards the drive shaft by means of a bolt, which causes the socket to become squeezed between the impeller and the drive shaft. Thus, by means of friction the socket will transmit a rotational motion from the drive shaft to the impeller. However, high initial starting torque or other types of sudden jerks, which may occur especially when the pump operates in heavily polluted liquids, tend to cause a small slip between the impeller and the socket and/or between the drive shaft and the socket. Consequently, the different elements will wear and the interconnection of the impeller and the drive shaft will deteriorate, the consequence being that the transmission of rotational motion may be lost.